#! /usr/bin/perl

# ex:ts=8 sw=4:
# $OpenBSD: extract_chunks,v 1.2 2014/09/20 09:35:54 espie Exp $
#
# Copyright (c) 2014 Marc Espie <espie@openbsd.org>
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

# modern packages are "chunked" archives, composed of several gzip files
# this script can extract each chunk for further analysis, as it is
# difficult using plain old gunzip to do something like that.

use strict;
use warnings;
use IO::Uncompress::AnyUncompress qw($AnyUncompressError);
use File::Basename;

for my $f (@ARGV) {
	my $z;
	unless ($z = IO::Uncompress::AnyUncompress->new($f)) {
		print STDERR "Bad compressed file $f: $AnyUncompressError\n";
		next;
	}

	my $buffer;
	my $length = 1024 * 1024;
	my $stem = basename($f, ".tgz");
	my $i = 0;

	while (1) {
		$i++;
		# build chunk name in the current directory
		my $out ="$stem.tar.".sprintf("%04d", $i);
		open my $fh, ">", $out or die "Can't open chunk $out: $!";
		while (1) {
			my $r = $z->read($buffer, $length);
			if ($r < 0) {
				print STDERR "Error reading from $f: ",
				    $AnyUncompressError, "\n";
			}
			if ($r <= 0) {
				last;
			}
			syswrite $fh, $buffer, $r;
		}
		close $fh;
		my $s = $z->nextStream;
		if ($s == -1) {
			print STDERR "Error switching to next stream of $f:",
			    $AnyUncompressError, "\n";
		}
		if ($s != 1) {
			last;
		}
	}
}